Conventionally, there has been known an air-condition remote control system which enables a vehicle user to start an air conditioner of a vehicle in advance before getting into the vehicle through remote control, to thereby perform pre-air-conditioning of the vehicle cabin. For example, in a system proposed in Patent Document 1, an instruction for operating an air conditioner of a vehicle is transmitted from a cellular phone to an onboard monitor apparatus via a base station. Upon receipt of the operation instruction, the onboard monitor apparatus determines whether or not the voltage of an onboard battery is equal to or higher than a predetermined voltage at or above which the air conditioner can operate. When the voltage of the onboard battery is equal to or higher than the predetermined voltage, the onboard monitor apparatus operates the air conditioner. Subsequently, the onboard monitor apparatus provides the cellular phone with information representing whether or not the air conditioner has started its operation.